The present invention relates to hydrolyzable and polymerizable silanes, methods of making them and methods of using them to make silicic acid polycondensates and/or -heteropolycondensates and polymerizates and/or heteropolymerizates.
Hydrolyzable, organically modified silanes have various applications in the manufacture of scratch-resistant coatings for different substrates, for making filling materials, adhesive and sealing materials or molded bodies. In those applications the silanes, either alone or in mixtures with each other or in the presence of additional hydrolyzable and/or condensable components, are hydrolytically condensed. The final hardening occurs thermally, photochemically, covalent-nucleophilically or is redox induced.
Thus scratch resistant coatings which are described, for example, in German Published Patent Application DE 3407087 C2 are formed by hydrolytic condensation of a mixture which, among other things, comprises, a hydrolyzable titanium or zirconium compound MR.sub.4 and a hydrolyzable, organo-functional silane EQU R'.sub.m (R"Y).sub.n SiX.sub.4-m-n,
wherein R represents, e.g., halogen, hydroxy, alkoxy and acyloxy groups and R' represents, e.g., alkyl or alkenyl, R" represents, e.g., alkylene or alkenylene, and X represents a hydrolyzable group.
Adhesive and sealing materials are described in German Published Patent Application DE 3536716 A1 which could be obtained by hydrolytic condensation of one or more organosilanes of the general formula R.sub.m SiX.sub.4-m and, as needed, one or more of the compounds of the formula SiX.sub.4 and/or R.sub.n (R"Y).sub.p SiX.sub.4-n-p, wherein R and R" are independently, e.g., an alkyl group, alkenyl group, aryl group, alkylaryl group, an arylalkyl group, an alkenylaryl group or an arylalkenyl group; X, e.g., is hydrogen, halogen, a hydroxy group, an alkoxy group or an acyloxy group; and Y, e.g., represents a halogen or an unsubstituted or substituted amino, amide, aldehyde, alkylcarbonyl, carboxy, hydroxy, mercapto or cyano group.
Commercial silanes with reactive double bonds are known, such as (meth)acryloxysilanes of the following formula: EQU CH.sub.2 .dbd.CR--CO--O--(CH.sub.2).sub.3 --SiX.sub.3
wherein R is hydrogen or methyl and X represents, e.g., a halogen or alkoxy group. These silanes are hydrolyzable and polymerizable and can be used for manufacture of the above-described systems. They offer the great advantage that the resultant coating, the resultant filling material, adhesive material, sealing material or the resultant molded body can be hardened by polymerization at the reactive double bond thermally and/or photqchemically.
In all the above systems it is disadvantageous that a volume decrease occurs in the polymerization, i.e. a so-called hardening shrinkage occurs, which also leads to stresses and strains in the coating, or in the resultant filling material, adhesive material, sealing material or the resultant molded body, and/or to a loss of bulk adherence. These stresses and strains can lead to macroscopic break-up, i.e. to tears or to pieces breaking off, as for example to optical interference phenomenon (local changes in the index of refractions, interference sites), to reduced mechanical stability, to surface structures, etc. The loss of bulk adherence is particularly troublesome for formation of molded bodies (e.g. in injection molding) and in bulk molding (optical gratings, etc).
Hydrolyzable and polymerizable silanes, which have one or more spiro group and are hydrolytically condensable alone, or together with other hydrolyzable components, and are hardened by ring opening followed by polymerization, are described in German Published Patent Application DE 4125201 C1. These ring openings of course counteract shrinkage on hardening. Inspite of that, there is still a need for further development e.g. to improve biological degradability.